The invention relates to the technical field of window cleaning devices, in particular to a window cleaning device with the power line length adjustable.The window cleaning device comprises a host, a power line, a safety rope, an adjustable fixing device and a power supply; the power line is connected with the host and the power supply; the adjustable fixing device is fixedly arranged at any position of the power line in a sleeving mode; one end of the safety rope is movably arranged on the portion, between the host and the adjustable fixing device, of the power line in a sleeving mode, and the other end of the safety rope is fixed at a determined position in a room.According to the window cleaning device, the length of the power line used by the host is adjusted by adjusting the position where the adjustable fixing device is fixed on the power line, so that the maximum working distance of the host is the sum of the length of the safety rope and the distance between the adjustable fixing device and the host.The window cleaning device with the power line length adjustable has the advantages that the structure is simple, the cost is low, the power line length is convenient to adjust, the loosening phenomenon of a connector for externally connecting the safety rope with the power line can be avoided, and convenience is brought to a user.